The present invention relates to a process for preparing 2'-deoxy-.beta.-adenosine having the following formula [I]: ##STR1##
2'-deoxy-.beta.-adenosine obtained by the present invention is a raw material of the compound which is useful as a medicine, and it is a constituent of deoxyribonucleic acid, which is a gene. Consequently, the demand for 2'-deoxy-.beta.-adenosine is increasing with the advance of genetic engineering in recent years.
Conventionally 2'-deoxy-.beta.-adenosine is prepared from natural deoxyribonucleic acid by decomposing it with enzymes. However, such process is not fit for industrial preparation, because the raw material is restricted in the resources thereof.
The following processes as "chemical synthesis" are known:
(1) Derivatives of adenine are allowed to condense with derivatives of 2-deoxy-D-erythro-pentofuranose to obtain an equivalent mixture of anomers and then .beta.-type compound is separated. [Biochimica et Biophysica Acta, 145, 221(1967)].
(2) Hydroxyl group of 2-position of adenosine as a raw material is eliminated to obtain 2'-deoxy-.beta.-adenosine. [Journal of American Chemical Society, 105, 4059 (1983); Journal of Organic Chemistry, 47, 485 (1982)].
In the process of the above (1), it is complicated to separate .beta.-type compound desired from a mixture of anomers, and in the process of the above (2), poisonous tin compounds have to be used. Therefore, these processes are not industrial.
Recently, synthesis of 2'-deoxy-.beta.-adenosine has been reported that sodium salt of 6-chloropurine derivative and 1-chloro-2-deoxy-3,5-di-O-p-toluoyl-.alpha.-D-erythro-pentofuranose are subjected to .beta.-selective condensation. [Journal of American Chemical Society, 106, 6379 (1984); TOKKYO-KOKAI-KOHO (18-month Publication of Unexamined Patent Application) SHOWA 61(1986)-106594].
In this process, there are defects that: (1) 6-chloropurine derivative used as a raw material is expensive; (2) sodium hydride used in preparation of a sodium salt is dangerous; (3) in substitution of a chloro group with an amino group, heating and pressurization are required. Consequently, conventional processes are not industrially preferable.